Development of a non-target screening workflow for the evaluation of micropollutants fate during oxidation processes

Non-target screening (NTS) is of great interest for environmental monitoring because it enables the screening of numerous pollutants, including unknown products. However, methods to identify unknowns are still time-consuming and only deal with a limited portion of the signal. The objective of this work was to develop a NTS workflow that enables an automated and comprehensive characterization of the evolution of a sample during water treatment, using high-resolution mass spectrometry (HRMS). Considering different conditions (matrix, micropollutant concentration), methods based on the obtention of raw formulas of detected compounds were evaluated. Oxidation processes (chlorination, UV/H2O2 or ozonation) were applied to wastewater samples to obtain contrasted HRMS fingerprints and to assess the relevance of the workflow to characterize transformation products (TPs). Batch experiments were conducted to confirm the ability of such a workflow to properly characterize the modification of the sample. Different extraction methods were also applied to enlarge the range of detected TPs. Preliminary results show that the workflow is able to rapidly compare the fingerprints of the samples (e.g., highlighting the presence of oxidation products characterized by the incorporation of oxygen atoms into compounds). The applied workflow also enables the tracking and identification of specific TPs formed by oxidation.